68000 Microcode Division

About

This repository contains an analysis of the 68000 DIVU and DIVS instructions at the micro- and nanocode level as presented in US patents 4325121 and 4296469.

The motivation was to understand the correct timings for the instructions in question.

The repository comprises

1. A trimmed down 68000 microcode emulator for the DIVU instruction and associated unit tests
2. A trimmed down 68000 microcode emulator for the DIVS instruction and associated unit tests
3. Notes outlining the basics of 68000 micro- and nanocodes
4. Notes outlining the workings of the DIVU and DIVS instructions

Code

This project uses CMake as the build tool and googletest for testing. To build and run the tests:

mkdir my_build_directory
cd my_build_directory
cmake -G <your favourite generator> /path/to/this/repository
cmake --build .
ctest --verbose

Notes

The notes in this repository are presented in the suggested reading order

1. 68000 microcode primer
2. 68000 unsigned division
3. 68000 signed division
4. Bibliography

3rd party documents

The documents in the docs-third-party folder are copyright their original authors.

In particular, the searchable document for the US patent appendix is the work of Exodus Megadrive emulator (Nemesis), without which this project would have taken longer.

The documents are included here for preservation purposes only.

Licence and copyright

68000 Microcode Division is licensed under MIT. Copyright 2023 Richard Brown.